1. Statement of the Technical Field
The invention is directed to a mobile/portable radio system. In particular, the invention is directed to a system including a fully functional portable radio that can also remotely control a separate mobile radio.
2. Description of the Related Art
Land Mobile Radio (LMR) systems are in widespread use across the world. These systems are often used by fire, police, and other first responder organizations for communication between organization members. LMR systems are also used by many commercial organizations to dispatch and communicate with vehicles and people. LMR systems often include one or more central dispatch offices, but individuals can also communicate with one another without the assistance of a dispatch office.
LMR systems typically provide point-to-multipoint communications between members of a group using the system. A channel is selected by the user to determine the radio frequency that the LMR device will operate at. Transmission and reception may occur at the same frequency. Alternatively, the selected channel may define separate transmit and receive frequencies. A push-to-talk (PTT) button is pressed on the radio equipment to open communication on a selected channel. A user can then transmit a message, typically in the form of voice, on the selected channel. Any members of the group that are monitoring the selected channel will receive the message. The message can also be in the form of data entered with a keyboard or dual tone multi frequency (DTMF) keypad.
One or more repeaters are often included in the communication system to allow users distributed over a wide geographical area to communicate with one another. A repeater receives a signal and retransmits it at a higher power, thus increasing the range of the communication system. Although repeaters are often used, LMR equipment can also operate in “talk-around” mode, which allows two or more devices to communicate without the use of a repeater.
More modern systems use a trunking protocol that allows multiple users and groups to share a single frequency channel. In a trunked system, a repeater or base station provides a control channel that individual devices monitor to determine which frequency bands to monitor and transmit on at any given moment. This protocol allows multiple talk groups to share the same frequency band without interfering with one another.
LMR equipment that is installed in a vehicle is usually referred to as a mobile radio. Because a mobile radio is powered by the vehicle's power system, battery life is generally not a concern. Therefore, mobile radios can transmit at a high power level. Mobile radios also generally have a large antenna attached directly to the vehicle to improve transmission and reception efficiency. Mobile radios may also include multiple antennas, e.g., diversity antenna structures, that increase transmission and reception reliability. However because mobile radios are fixed in a vehicle, they cannot be used by a user, e.g., a police officer, when the user is not in the vehicle.
LMR equipment that can be carried by an individual user is referred to as a portable radio. A portable radio is usually sized so as to be easily carried by a user. Portable radios are typically powered by a small rechargeable battery. Accordingly, battery life is a concern and portable radios are generally designed to transmit at a lower power than mobile radios. Additionally, due to size constraints, portable radios typically have smaller antennas than mobile radios and rarely accommodate multiple antennas. The operating range of a portable radio is therefore generally more limited than that of a mobile radio.
To overcome the range limitations associated with portable LMR equipment, a number of techniques have been developed. A simple RF repeater is sometimes used. The repeater, which is usually installed in a vehicle, amplifies the RF signals transmitted to and from the portable radio. This system has the advantage that it increases the range of the portable radio. Additionally, the portable radio may connect through a wired interface to a mobile radio to take advantage of the higher power transmitter of the mobile radio. Although these systems overcome some of the limitations of the portable radio, they require that the user physically have access to the mobile radio to change parameters such as the channel number and the RF power level.
Kenwood, a manufacturer of portable, mobile, and fixed location radios, has introduced a radio system known as SkyCommand that allows a portable radio to remotely control a High Frequency (HF) radio. However, the portable radio includes only a single radio interface that is used both for standalone communications and remote control of the HF radio. Thus, the portable radio must be either used as a remote control or a standalone radio and cannot seamlessly switch between the two modes of operation. Additionally, the communications link between the portable radio and the HF radio includes only rudimentary security features, such as the use of Continuous Tone-Coded Squelch System (CTCSS).
Similarly, to overcome the limitations of the mobile radio, simple remote control units have been developed. These units communicate with the mobile radio when the remote control is near to the vehicle. This provides the user with a limited level of mobility and allows the user to communicate even when not in the vehicle. However, these remote controls must be close to the vehicle to operate. When the remote control is too distant from the mobile radio, the user is unable to communicate. This is a significant limitation for users who need to leave the area of the mobile radio to perform their duties.
Therefore, there is need in the art for a radio system that provides robust security that allows a user to take advantage of the increased transmission range of a mobile radio when near the mobile radio but also allows the user seamlessly retain his or her ability to communicate even when distant from the mobile radio. The present invention satisfies these and other needs.